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Improving draft on a metal chimney

Improving draft on a metal chimney

If the metal chimney is poorly drafting, it allows smoke to enter the home instead of exhausting outside. In order to correct the problem, you should find out what is causing the drafting problem. Some of the causes include starting hot fire on a cold chimney, a too large firebox in relation to the chimney pipe or the chimney having incorrect height. Below are some of the methods of improving drafting.

Warming the chimney

If a cold chimney causes the drafting problem, warm it to allow the smoke to move from the firebox to the outside. Roll a newspaper piece and light one of its ends. Hold it below the chimney system, allow it to burn, and then drop it on the fireplace to burn completely. This will warm the chimney to pull the smoke up. Light the fire immediately.

Raising the height of the chimney

Poor drafting may be due to the chimney being short. You can correct this by increasing the height of the chimney. Using a ladder to reach the chimney, carefully add a metal chimney pipe to the current one by inserting the female side of the new pipe to the top end of the chimney. Return the chimney cap back on the chimney pipe and check if the draft is proper. Increasing the chimney height helps to increase draft. The bigger the percentage increase, the better the draft.

Correcting the size of the firebox

When the firebox is too large in relation to the chimney opening, it can cause drafting problems. The chimney may not take up all the smoke from the firebox. To get the measurements of the firebox, take its height and width and multiply them. Do the same with the chimney opening. Compare these two numbers. The firebox should be less than ten times the flue opening. For instance, if the firebox is 20 x 20 inches totaling to 400 and chimney is 6 x 6 inches totaling 36, the firebox is more than ten times the opening by 40 inches. This means that the firebox needs to be reduced by 40 inches for proper drafting. This is done by installing a smoke guard. To get the height of the smoke guard, divide the inches to be reduced by the depth of the firebox. In this case, it is 40 inches divide by the firebox depth (20 inches) to get 2 inches.


Cut an aluminum foil of firebox width-20 inches and 2 inches height. Tape it temporarily at the front edge of the firebox. This is a foil smoke guard. Light fire to determine if there is proper drafting. If it is working, get a permanent smoke guard and install it. Note that the measurements provided here are just for example purposes. You will need to take the measurements of the firebox and the chimney opening and use them to get the measurements of the smoke guard.

Raise the fire grate


You can raise the grate using a brick. If after raising the drafting problem is solved, then you should raise the fire grate permanently using firebricks.

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